This article was first published on 8 October 2025 and has now been updated.
In front of me, the cone of light from my lamp dances from left to right and back again. It cuts through the darkness of the mountain world like a metronome. My lungs are burning, shovelling the oxygen from the cold morning air into my over-acidified muscles at maximum speed. I powerfully pump out high wattages while pedalling in a cradle position.
Then: the taste of blood mixes with my saliva and the twitching of the light becomes more uncoordinated. My right thumb desperately feels for the gear lever, but there's nothing there. My bike has no gears, no transmission, no crawling gear. The chain only runs over a single sprocket. At the moment, that's simply not enough.
My mission has only just begun and doubt is already driving its venomous fangs into my motivation like a deadly snake. Cycling from the source of a river has the advantage that most of the way is downhill. However, there is rarely a hotel where the water gushes out of the rock. That's why I have to cycle uphill first.
The Isar rises at an altitude of 1162 metres above the small Austrian village of Scharnitz, where I clicked in at half past five in the morning. I have to carry my bike over narrow root paths for the last few metres. Luckily it's only lightly loaded. I already had an inkling that I would have to ride standing up a lot and didn't want to make the leverage work any harder.
After the many tributaries have branched off, the actual Isar gurgles out of several springs here in the Hinterautal valley as a small mountain stream between the roots. A quick souvenir photo, then I have to move on. The loud screeching of my freewheel breaks the silence.
I can no longer pedal along. My gear is too small now. Instead, I sit on the top tube to minimise my exposure to the braking wind. Behind the next bend, the clouds open up. Like a mirage, a window opens in the grey to reveal a sunlit rocky peak. I have a feeling: this is going to be a good day!
Don't stop for long - keep going!
The first few kilometres fly by quickly. Mittenwald and Wallgau with their idyllic wooden houses pass me by and in no time at all I'm on the toll road to Vorderriß, where the Isar mixes with the ice-cold waters of the Rißbach. Most of my route is on gravel. Here in the narrow valley it can also be tarmac.
Cyclists can pass through free of charge and the scenic panorama of crystal-clear water and the imposing foothills of the Alps is all the better. It can get pretty crowded here on nice weekends, but everything is still peaceful.
My singlespeed project is not the first Isar story to make it into BIKE magazine. In 2001, colleagues reported on the "Canada of Bavaria", surfing down the gravel slopes of the surrounding mountains on their freeride bikes and camping right on the banks of the river with a campfire and guitar music.
Ten years later, another Isar story. Now the printing of a campfire picture has cost 40,000 euros in fines. Since the natural jewel of the young Isar has been attracting more and more tourists, the protection standards have also been raised. I'd rather drive on.
In any case, I personally don't think much of the "overnighter" trend concept. Lashing all that bikepacking gear to your bike just to illegally lay down somewhere for a single night after a few lousy kilometres? No thanks, I'd rather cycle the 300 kilometres in one go!
It would be inviting here, because next to the "Canada of Bavaria" lies the "Caribbean of Bavaria". The turquoise blue colour of the Sylvenstein reservoir is a popular photo motif. But there is a rational calculation behind the idyll. The reservoir holds up to 125 billion litres of water, which is intended to protect the metropolis of Munich from flooding.
Here, at this bastion of civil defence, I meet up with photographer Georg again. By the time we have all the pictures in the box, the sat nav shows half past eleven. Anxiety spreads through me and hits my stomach. If I want to complete the remaining 250 kilometres in a reasonable amount of time, I have to hurry. So I get on the pedals and shoot through the cycle tunnel down to Lenggries.
100 times over the dyke
Shortly before Bad Tölz, I catch up with a gravel biker. He immediately senses the scent: "What kind of gears is that?" he calls out questioningly into the wind. "No gears!" I reply briefly. "What do you mean, no gears?" comes the prompt question. Riding a singlespeed requires some explanation.
When the many small ramps before Wolfratshausen almost pull the plug on me, I question the concept of the entry mountain bike itself. Of course there are rational reasons: Less wear and tear, less weight, less complexity. "If it's not on, it can't break" is an old BMXer saying.
In truth, however, single-speed cycling is also a form of protest. Against the complication and mechanisation of the bicycle. Against the electrification of an inherently perfect machine and the toxic pressure of sporting self-optimisation.
At the Singlespeed Olympics, the starting numbers are only handed out at two o'clock in the morning at the punk rock concert to those who can prove that they have a certain level of beer in their blood. At the Singlespeed World Championships, the medal is not handed out but tattooed. Singlespeed is pure rebellion.
At the Isar Canal before Grünwald, I weave my way through the cycle tourists on their heavily laden e-bikes. Five to seven daily stages are advertised for the entire Isar cycle path on the relevant tour portals. The recommendation probably includes at least thirty gears.
Finally, the route leads to the high banks of the Isar. The climb with my one gear feels endlessly long. The power of every pedal stroke of the 32-to-13 gear ratio has to go through my back. I wish I'd booked a few extra lessons at the gym! I actually thought I would start in the Karwendel and just roll downhill to Deggendorf. There are only just over 1000 metres of elevation gain over the 300 kilometres.
But singlespeed is also exhausting when you have to go up and down the dyke 100 times. I take the last sip of the Isar spring water, which I have now transported 140 kilometres in my water bottle. Maybe it will give me the power of the river.
On the road among cyclists
Munich's fast cycle route along the Isar is notorious. "Kamikaze cyclists" and "Radl-Rambos" have been the subject of many a CSU regional meeting. The river axis through the state capital is home to everything powered by a pedal crank.
I overtake a guy in a cowboy hat on his fatbike. A hit song is blaring from a jukebox attached to the frame. Around the next bend, I have to dodge a cargo bike whose half-strong pilot only has eyes for his smartphone. Then a slender racing cyclist flies past me at 40 kilometres an hour.
When the hustle and bustle finally comes to an end, I have to get out of the saddle briefly at a quiet corner. The first signs of fatigue make themselves felt: My eyes are slightly swollen shut, my leg muscles ache and don't want to relax at all. Singlespeed biking is like involuntary interval riding. Right now, the interval training has been going on for eight and a half hours.
The Isar has many faces. As far as Munich, it flows bright blue and wild, like a real mountain river. Beyond the city limits, the characteristic gravel banks become fewer and fewer and the colour changes to a green-brown. Soon the water flows straightened through alluvial forests.
On the satellite map, you can see that the Isar connects Upper and Lower Bavaria here like a green ribbon, cutting through a largely flat agricultural desert. I'm now curving northwards in a dead straight line between old trees. My legs are rotating surprisingly easily again, but my head is struggling with the fact that I've only completed a good half of my route.
From Moosburg onwards, the power of the Isar is increasingly used to generate energy and the track criss-crosses between the transformer stations. For singlespeed riding, it is essential to carry speed through bends and push over crests. At the moment, I'm completely missing this dynamic. I'm tired.
Why a singlespeed bike?
I have to stop for a few minutes at the middle Isar reservoirs. Hundreds of migratory birds float on the surface of the water here in the nature reserve. Just like me, they are taking a break here on their long journey. As I watch the wild geese and swans in the low sun, I let my mind wander. The most frequently asked question to single-speed bikers is: "Why?", usually accompanied by narrowed eyes in disbelief and a sceptical shake of the head.
My standard answer is: "To increase stimulation!" But that's actually wrong. The opposite is the case. A single-speed disciple friend of mine once dubbed mountain biking with just one gear "the fascia roll for the brain". Just steering and pedalling, nothing else. The monotonous pedalling squeezes the thoughts of everyday life out of your head and leaves you feeling pleasantly empty - and a little sore, but that's okay.
In Landshut, I top up my food and water supplies one last time at the supermarket. My body needs around 12,000 calories and about eleven litres of fluid on this day. My muscles and organs will have to recover from the strain for days to come.
It's dusk and I switch on my headphones in addition to the lighting system. As the light fades and gives way to darkness, there is less distraction for the eyes. Without the change of scenery, the human system focuses more on exhaustion and the mental side of the challenge intensifies.
I then need music to give my head a different sensory stimulus. So the Toten Hosen whip me up for the final 80 kilometres: "Are you going to change your life or would you rather not? No matter what you do, it always ends the same!"
Piece of evidence
It's a pitch-black night. I constantly have to stop and eat another bar. I'm constantly wincing when a frog jumps across the gravel track, startled by my light. My energy reserves are depleted. The last two hours feel like ten.
Finally, just before midnight, the Bavarian Forest stands out against the starry sky. There, that must be Deggendorf! On a hill above the town, the lights of the local hospital light my way. That's where the helicopter dropped me off a good three years ago after I shattered my left knee into twelve pieces.
"You'll never be able to cycle like you used to." That was one of the first sentences I heard from the doctors at the time. Defiance mingles with my pedalling and masks the tiredness. I bravely push up onto the embankment one last time and roll over the Danube bridge not far from the mouth of the Isar. I wanted to prove to myself that one gear and a healthy leg are enough as long as a clear head is involved. Mission accomplished.
Balance sheet
- Distance: 318.8 km
- Height gain: 1035 m
- Journey time: 14:26 h
- Average speed: 22.1 km/h
- Temperature range: 9-24° C
- Calorie consumption: 12,101 kcal
Jan Timmermann
Editor
